Johnson, who captained England to World Cup glory two years ago, is keen to see rugby broaden its horizons and backed Japan's bid ahead of those from established powers New Zealand and South Africa.
"Japan is a big rugby-playing nation and giving the country the World Cup could take the game to a new level globally," said Johnson.
"It would be a new venue for a lot of rugby supporters - a whole new experience for everyone connected with the tournament.
"Japan showed during the football World Cup that they can handle the occasion and I think they'll do it brilliantly in 2011.
"Japan is an amazing place and I'm sure thousands of fans would have a fantastic experience."
Johnson was joined at Monday's official launch by former England team-mate Jason Leonard and Peter Wheeler, the Leicester chief executive.
Wheeler said: "I played my first game in an England shirt against Japan at Osaka. I didn't visit Japan again until earlier this year when I accompanied Martin Johnson to a dinner in his honour in Tokyo.
"A short presentation was screened at it on Japan's 2011 bid - and it impressed us both.
"Not just the details of the grounds and infrastructure that would be used, but also with its vision of how Japan 2011 would help the development of rugby world wide.
"I was in New Zealand for the 1987 and also South Africa in 1995 and I know they could both hold a great tournament again.
"But so could Japan - and it can so do much more too."
The International Rugby Board will announce its decision on the host nation for the 2011 World Cup on November 17.